Observations of turbulent mixing in the Bohai Sea during weakly stratified period

Xu Pengzhao; Yang Wei; Zhao Liang; Wei Hao; Nie Hongtao

doi:10.3969/j.issn.0253-4193.2020.03.001

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Xu Pengzhao，Yang Wei，Zhao Liang, et al. Observations of turbulent mixing in the Bohai Sea during weakly stratified period[J]. Haiyang Xuebao，2020, 42(3)：1–9，doi:10.3969/j.issn.0253−4193.2020.03.001

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Observations of turbulent mixing in the Bohai Sea during weakly stratified period

doi: 10.3969/j.issn.0253-4193.2020.03.001

1.
School of Marine Science and Technology, Tianjin University, Tianjin 300072, China
2.
College of Marine and Environmental Sciences, Tianjin University of Science and Technology, Tianjin 300457, China

Received Date: 2019-01-28
Rev Recd Date: 2019-08-18

Available Online: 2020-11-18

Publish Date: 2020-03-25

Abstract

Abstract

Based on the direct turbulence observations in the Bohai Sea during September 2017, this study investigates the spatial distribution of turbulent mixing in the Bohai Sea and the associated influencing factors. The water column was weakly stratified during the observation period. As influenced by the freshwater input from Yellow River, relatively warm and fresh water was found in the Laizhou Bay. The typical south-north dual-core cold bottom water structure still exited in the central Bohai Sea during the observation period. The observed turbulent kinetic energy (TKE) dissipation rate ε ranged from 10⁻⁹ to 10⁻⁵ W/kg and statistically satisfied the lognormal distribution. Intensified mixing was found at the nearshore region of the Liaodong Bay and the Bohai Bay. The corresponding vertical eddy diffusivity was about 10⁻⁶～10⁻² m²/s. In the vertical direct direction, strong mixing occurred near the sea surface and bottom layers. Further analysis shows that the station-averaged TKE dissipation rate are positively related to the wind speed and barotropic tidal velocity. On the other hand, the dissipation rate and buoyancy frequency N satisfied the power function relationship of $\varepsilon = 2.0 \times {10^{ - 8}} + 3.0 \times {10^{ - 7}}{({N^2}/N_0^2)^{ - 5}}$ indicating that inhibition effect of stratification on turbulent mixing.
- turbulent kinetic energy dissipation rate,
- vertical eddy diffusivity,
- Bohai Sea

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